Sarcoplasmic Reticulum Calcium-Transporting ATPases: Calcium-transporting ATPases that catalyze the active transport of CALCIUM into the SARCOPLASMIC RETICULUM vesicles from the CYTOPLASM. They are primarily found in MUSCLE CELLS and play a role in the relaxation of MUSCLES.Sarcoplasmic Reticulum: A network of tubules and sacs in the cytoplasm of SKELETAL MUSCLE FIBERS that assist with muscle contraction and relaxation by releasing and storing calcium ions.Plasma Membrane Calcium-Transporting ATPases: Calcium-transporting ATPases found on the PLASMA MEMBRANE that catalyze the active transport of CALCIUM from the CYTOPLASM into the extracellular space. They play a role in maintaining a CALCIUM gradient across plasma membrane.Calcium-Transporting ATPases: Cation-transporting proteins that utilize the energy of ATP hydrolysis for the transport of CALCIUM. They differ from CALCIUM CHANNELS which allow calcium to pass through a membrane without the use of energy.Calcium: A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.Endoplasmic Reticulum: A system of cisternae in the CYTOPLASM of many cells. In places the endoplasmic reticulum is continuous with the plasma membrane (CELL MEMBRANE) or outer membrane of the nuclear envelope. If the outer surfaces of the endoplasmic reticulum membranes are coated with ribosomes, the endoplasmic reticulum is said to be rough-surfaced (ENDOPLASMIC RETICULUM, ROUGH); otherwise it is said to be smooth-surfaced (ENDOPLASMIC RETICULUM, SMOOTH). (King & Stansfield, A Dictionary of Genetics, 4th ed)Rabbits: The species Oryctolagus cuniculus, in the family Leporidae, order LAGOMORPHA. Rabbits are born in burrows, furless, and with eyes and ears closed. In contrast with HARES, rabbits have 22 chromosome pairs.Ryanodine Receptor Calcium Release Channel: A tetrameric calcium release channel in the SARCOPLASMIC RETICULUM membrane of SMOOTH MUSCLE CELLS, acting oppositely to SARCOPLASMIC RETICULUM CALCIUM-TRANSPORTING ATPASES. It is important in skeletal and cardiac excitation-contraction coupling and studied by using RYANODINE. Abnormalities are implicated in CARDIAC ARRHYTHMIAS and MUSCULAR DISEASES.Caffeine: A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine's most notable pharmacological effect is as a central nervous system stimulant, increasing alertness and producing agitation. It also relaxes SMOOTH MUSCLE, stimulates CARDIAC MUSCLE, stimulates DIURESIS, and appears to be useful in the treatment of some types of headache. Several cellular actions of caffeine have been observed, but it is not entirely clear how each contributes to its pharmacological profile. Among the most important are inhibition of cyclic nucleotide PHOSPHODIESTERASES, antagonism of ADENOSINE RECEPTORS, and modulation of intracellular calcium handling.Calsequestrin: Acidic protein found in SARCOPLASMIC RETICULUM that binds calcium to the extent of 700-900 nmoles/mg. It plays the role of sequestering calcium transported to the interior of the intracellular vesicle.Ryanodine: A methylpyrrole-carboxylate from RYANIA that disrupts the RYANODINE RECEPTOR CALCIUM RELEASE CHANNEL to modify CALCIUM release from SARCOPLASMIC RETICULUM resulting in alteration of MUSCLE CONTRACTION. It was previously used in INSECTICIDES. It is used experimentally in conjunction with THAPSIGARGIN and other inhibitors of CALCIUM ATPASE uptake of calcium into SARCOPLASMIC RETICULUM.Muscles: Contractile tissue that produces movement in animals.Adenosine Triphosphatases: A group of enzymes which catalyze the hydrolysis of ATP. The hydrolysis reaction is usually coupled with another function such as transporting Ca(2+) across a membrane. These enzymes may be dependent on Ca(2+), Mg(2+), anions, H+, or DNA.Myocardium: The muscle tissue of the HEART. It is composed of striated, involuntary muscle cells (MYOCYTES, CARDIAC) connected to form the contractile pump to generate blood flow.Calcium-Binding Proteins: Proteins to which calcium ions are bound. They can act as transport proteins, regulator proteins, or activator proteins. They typically contain EF HAND MOTIFS.Ca(2+) Mg(2+)-ATPaseAdenosine Triphosphate: An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.Calcium Signaling: Signal transduction mechanisms whereby calcium mobilization (from outside the cell or from intracellular storage pools) to the cytoplasm is triggered by external stimuli. Calcium signals are often seen to propagate as waves, oscillations, spikes, sparks, or puffs. The calcium acts as an intracellular messenger by activating calcium-responsive proteins.Myocardial Contraction: Contractile activity of the MYOCARDIUM.Calcium Channels: Voltage-dependent cell membrane glycoproteins selectively permeable to calcium ions. They are categorized as L-, T-, N-, P-, Q-, and R-types based on the activation and inactivation kinetics, ion specificity, and sensitivity to drugs and toxins. The L- and T-types are present throughout the cardiovascular and central nervous systems and the N-, P-, Q-, & R-types are located in neuronal tissue.Kinetics: The rate dynamics in chemical or physical systems.Ruthenium Red: An inorganic dye used in microscopy for differential staining and as a diagnostic reagent. In research this compound is used to study changes in cytoplasmic concentrations of calcium. Ruthenium red inhibits calcium transport through membrane channels.Muscle Proteins: The protein constituents of muscle, the major ones being ACTINS and MYOSINS. More than a dozen accessory proteins exist including TROPONIN; TROPOMYOSIN; and DYSTROPHIN.Myocytes, Cardiac: Striated muscle cells found in the heart. They are derived from cardiac myoblasts (MYOBLASTS, CARDIAC).Muscle, Skeletal: A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.Sodium-Calcium Exchanger: An electrogenic ion exchange protein that maintains a steady level of calcium by removing an amount of calcium equal to that which enters the cells. It is widely distributed in most excitable membranes, including the brain and heart.Magnesium: A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.Thapsigargin: A sesquiterpene lactone found in roots of THAPSIA. It inhibits CA(2+)-TRANSPORTING ATPASE mediated uptake of CALCIUM into SARCOPLASMIC RETICULUM.Proton-Translocating ATPases: Multisubunit enzymes that reversibly synthesize ADENOSINE TRIPHOSPHATE. They are coupled to the transport of protons across a membrane.Egtazic Acid: A chelating agent relatively more specific for calcium and less toxic than EDETIC ACID.Excitation Contraction Coupling: A process fundamental to muscle physiology whereby an electrical stimulus or action potential triggers a myocyte to depolarize and contract. This mechanical muscle contraction response is regulated by entry of calcium ions into the cell.Microsomes: Artifactual vesicles formed from the endoplasmic reticulum when cells are disrupted. They are isolated by differential centrifugation and are composed of three structural features: rough vesicles, smooth vesicles, and ribosomes. Numerous enzyme activities are associated with the microsomal fraction. (Glick, Glossary of Biochemistry and Molecular Biology, 1990; from Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)Muscle Contraction: A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.Sarcolemma: The excitable plasma membrane of a muscle cell. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)Calcium Channels, L-Type: Long-lasting voltage-gated CALCIUM CHANNELS found in both excitable and nonexcitable tissue. They are responsible for normal myocardial and vascular smooth muscle contractility. Five subunits (alpha-1, alpha-2, beta, gamma, and delta) make up the L-type channel. The alpha-1 subunit is the binding site for calcium-based antagonists. Dihydropyridine-based calcium antagonists are used as markers for these binding sites.Tetracaine: A potent local anesthetic of the ester type used for surface and spinal anesthesia.Heart Ventricles: The lower right and left chambers of the heart. The right ventricle pumps venous BLOOD into the LUNGS and the left ventricle pumps oxygenated blood into the systemic arterial circulation.Biological Transport, Active: The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.Procaine: A local anesthetic of the ester type that has a slow onset and a short duration of action. It is mainly used for infiltration anesthesia, peripheral nerve block, and spinal block. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1016).Muscle Fibers, Skeletal: Large, multinucleate single cells, either cylindrical or prismatic in shape, that form the basic unit of SKELETAL MUSCLE. They consist of MYOFIBRILS enclosed within and attached to the SARCOLEMMA. They are derived from the fusion of skeletal myoblasts (MYOBLASTS, SKELETAL) into a syncytium, followed by differentiation.Myofibrils: The long cylindrical contractile organelles of STRIATED MUSCLE cells composed of ACTIN FILAMENTS; MYOSIN filaments; and other proteins organized in arrays of repeating units called SARCOMERES .Dantrolene: Skeletal muscle relaxant that acts by interfering with excitation-contraction coupling in the muscle fiber. It is used in spasticity and other neuromuscular abnormalities. Although the mechanism of action is probably not central, dantrolene is usually grouped with the central muscle relaxants.Oxalates: Derivatives of OXALIC ACID. Included under this heading are a broad variety of acid forms, salts, esters, and amides that are derived from the ethanedioic acid structure.Intracellular Membranes: Thin structures that encapsulate subcellular structures or ORGANELLES in EUKARYOTIC CELLS. They include a variety of membranes associated with the CELL NUCLEUS; the MITOCHONDRIA; the GOLGI APPARATUS; the ENDOPLASMIC RETICULUM; LYSOSOMES; PLASTIDS; and VACUOLES.Dogs: The domestic dog, Canis familiaris, comprising about 400 breeds, of the carnivore family CANIDAE. They are worldwide in distribution and live in association with people. (Walker's Mammals of the World, 5th ed, p1065)Heart: The hollow, muscular organ that maintains the circulation of the blood.Malignant Hyperthermia: Rapid and excessive rise of temperature accompanied by muscular rigidity following general anesthesia.Vacuolar Proton-Translocating ATPases: Proton-translocating ATPases that are involved in acidification of a variety of intracellular compartments.Microscopy, Electron: Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.Phosphorylation: The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety.Membrane Potentials: The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).Vanadates: Oxyvanadium ions in various states of oxidation. They act primarily as ion transport inhibitors due to their inhibition of Na(+)-, K(+)-, and Ca(+)-ATPase transport systems. They also have insulin-like action, positive inotropic action on cardiac ventricular muscle, and other metabolic effects.Endoplasmic Reticulum Stress: Various physiological or molecular disturbances that impair ENDOPLASMIC RETICULUM function. It triggers many responses, including UNFOLDED PROTEIN RESPONSE, which may lead to APOPTOSIS; and AUTOPHAGY.Biological Transport: The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.Hydrogen-Ion Concentration: The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH = log 1/2[1/(H+)], where (H+) is the hydrogen ion concentration in gram equivalents per liter of solution. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Amino Acid Sequence: The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Binding Sites: The parts of a macromolecule that directly participate in its specific combination with another molecule.Vanadium: A metallic element with the atomic symbol V, atomic number 23, and atomic weight 50.94. It is used in the manufacture of vanadium steel. Prolonged exposure can lead to chronic intoxication caused by absorption usually via the lungs.Adenosine Diphosphate: Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position.Fluorescent Dyes: Agents that emit light after excitation by light. The wave length of the emitted light is usually longer than that of the incident light. Fluorochromes are substances that cause fluorescence in other substances, i.e., dyes used to mark or label other compounds with fluorescent tags.Cell Membrane: The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.Hydrolysis: The process of cleaving a chemical compound by the addition of a molecule of water.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.Ion Transport: The movement of ions across energy-transducing cell membranes. Transport can be active, passive or facilitated. Ions may travel by themselves (uniport), or as a group of two or more ions in the same (symport) or opposite (antiport) directions.Murexide: 5,5'-Nitrilodibarbituric acid ammonium derivative. Used as an indicator for complexometric titrations.Potassium: An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.Indoles: Benzopyrroles with the nitrogen at the number one carbon adjacent to the benzyl portion, in contrast to ISOINDOLES which have the nitrogen away from the six-membered ring.Muscle Fibers, Fast-Twitch: Skeletal muscle fibers characterized by their expression of the Type II MYOSIN HEAVY CHAIN isoforms which have high ATPase activity and effect several other functional properties - shortening velocity, power output, rate of tension redevelopment. Several fast types have been identified.Phosphates: Inorganic salts of phosphoric acid.Calcium Radioisotopes: Unstable isotopes of calcium that decay or disintegrate emitting radiation. Ca atoms with atomic weights 39, 41, 45, 47, 49, and 50 are radioactive calcium isotopes.Xanthenes: Compounds with three aromatic rings in linear arrangement with an OXYGEN in the center ring.Membranes: Thin layers of tissue which cover parts of the body, separate adjacent cavities, or connect adjacent structures.Protein Conformation: The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).Sodium-Potassium-Exchanging ATPase: An enzyme that catalyzes the active transport system of sodium and potassium ions across the cell wall. Sodium and potassium ions are closely coupled with membrane ATPase which undergoes phosphorylation and dephosphorylation, thereby providing energy for transport of these ions against concentration gradients.Endoplasmic Reticulum, Rough: A type of endoplasmic reticulum (ER) where polyribosomes are present on the cytoplasmic surfaces of the ER membranes. This form of ER is prominent in cells specialized for protein secretion and its principal function is to segregate proteins destined for export or intracellular utilization.Naphthalenesulfonates: A class of organic compounds that contains a naphthalene moiety linked to a sulfonic acid salt or ester.Fluorescein-5-isothiocyanate: Fluorescent probe capable of being conjugated to tissue and proteins. It is used as a label in fluorescent antibody staining procedures as well as protein- and amino acid-binding techniques.Papillary Muscles: Conical muscular projections from the walls of the cardiac ventricles, attached to the cusps of the atrioventricular valves by the chordae tendineae.Lasalocid: Cationic ionophore antibiotic obtained from Streptomyces lasaliensis that, among other effects, dissociates the calcium fluxes in muscle fibers. It is used as a coccidiostat, especially in poultry.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Cytosol: Intracellular fluid from the cytoplasm after removal of ORGANELLES and other insoluble cytoplasmic components.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Terpenes: A class of compounds composed of repeating 5-carbon units of HEMITERPENES.Spectrometry, Fluorescence: Measurement of the intensity and quality of fluorescence.Halothane: A nonflammable, halogenated, hydrocarbon anesthetic that provides relatively rapid induction with little or no excitement. Analgesia may not be adequate. NITROUS OXIDE is often given concomitantly. Because halothane may not produce sufficient muscle relaxation, supplemental neuromuscular blocking agents may be required. (From AMA Drug Evaluations Annual, 1994, p178)Isoproterenol: Isopropyl analog of EPINEPHRINE; beta-sympathomimetic that acts on the heart, bronchi, skeletal muscle, alimentary tract, etc. It is used mainly as bronchodilator and heart stimulant.Aequorin: A photoprotein isolated from the bioluminescent jellyfish Aequorea. It emits visible light by an intramolecular reaction when a trace amount of calcium ion is added. The light-emitting moiety in the bioluminescence reaction is believed to be 2-amino-3-benzyl-5-(p-hydroxyphenyl)pyrazine (AF-350).Models, Biological: Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.Golgi Apparatus: A stack of flattened vesicles that functions in posttranslational processing and sorting of proteins, receiving them from the rough ENDOPLASMIC RETICULUM and directing them to secretory vesicles, LYSOSOMES, or the CELL MEMBRANE. The movement of proteins takes place by transfer vesicles that bud off from the rough endoplasmic reticulum or Golgi apparatus and fuse with the Golgi, lysosomes or cell membrane. (From Glick, Glossary of Biochemistry and Molecular Biology, 1990)Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Rana pipiens: A highly variable species of the family Ranidae in Canada, the United States and Central America. It is the most widely used Anuran in biomedical research.Calcium Channel Blockers: A class of drugs that act by selective inhibition of calcium influx through cellular membranes.Sodium: A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.Microscopy, Confocal: A light microscopic technique in which only a small spot is illuminated and observed at a time. An image is constructed through point-by-point scanning of the field in this manner. Light sources may be conventional or laser, and fluorescence or transmitted observations are possible.Ventricular Function: The hemodynamic and electrophysiological action of the HEART VENTRICLES.Strontium: An element of the alkaline earth family of metals. It has the atomic symbol Sr, atomic number 38, and atomic weight 87.62.Electric Stimulation: Use of electric potential or currents to elicit biological responses.Inositol 1,4,5-Trisphosphate Receptors: Intracellular receptors that bind to INOSITOL 1,4,5-TRISPHOSPHATE and play an important role in its intracellular signaling. Inositol 1,4,5-trisphosphate receptors are calcium channels that release CALCIUM in response to increased levels of inositol 1,4,5-trisphosphate in the CYTOPLASM.